class Solution(object):
    def duplicateZeros(self, arr):
        """
        :type arr: List[int]
        :rtype: None Do not return anything, modify arr in-place instead.
        """
        ans = []
        length = len(arr)

        for a in arr:
            if a == 0:
                ans.append(a)
                ans.append(0)
            else:
                ans.append(a)
        return ans[0:length]


if __name__ == '__main__':
    print(Solution().duplicateZeros([1,2,3]))
